This application is related to Japanese Patent Application No. 2000-219010 filed on Jul. 19, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an inside/outside air switching device using a rotary door as an inside/outside air switching door. More particularly, the present invention relates to a seal structure of the inside/outside air switching door in an inside air mode.
2. Description of Related Art
A conventional rotary-type inside/outside air switching door is formed into a gate shape having a rotation shaft inserted into both bearing holes, an outer wall plate extending in a rotation direction around the rotation shaft, and both side wall plates connecting the outer wall plate and both axial ends of the rotation shaft. Further, a packing member is provided in periphery portions of the side wall plate and the outer wall plate, and a seal surface is provided on an inside/outside air switching box to have a shape corresponding to the packing member. In the inside/outside air switching device, for obtaining a seal function between the inside/outside air switching door and the inside/outside air switching box, the packing member is pressed to the seal surface in the rotation direction of the rotation shaft. On the other hand, in the axial direction of the rotation shaft, a clearance is provided between a part of the side wall plates around the rotation shaft and an inner surface of the inside/outside air switching box, for rotating the inside/outside air switching door.
However, in an inside air mode where the inside/outside air switching door closes an outside air suction port of the inside/outside air switching box and closes an outside air suction port of the inside/outside air switching box, air pressure at a side of the outside air suction port of the rotary door becomes higher due to dynamical pressure (ram pressure) in a vehicle travelling. Accordingly, in this seal structure of the inside/outside air switching door, because the clearance is provided between the part of the side wall plate around the rotation shaft and the inner surface of the inside/outside air switching box, outside air may be leaked due to the dynamical pressure in the vehicle traveling. Thus, in the inside air mode, outside air may be mixed into inside air within the inside/outside air switching box.
In view of the foregoing problems, it is an object of the present invention to provide an inside/outside air switching device with a rotary door, which prevents a leakage of outside air from the inside/outside air switching door into an inside/outside air switching box in an inside air mode.
According to the present invention, in an inside/outside air switching device, a rotary door for selectively opening and closing an inside air suction port and an outside air suction port is disposed in an inside/outside air switching box to be rotatable around a rotation center axial line, and a seal member for sealing the inside/outside air switching box in an axial direction is provided at a position around the rotation center axial line. The rotary door includes an outer wall plate extending in the rotation direction of the rotary door, and both side wall plates extending from both end portions of the outer wall plate in an axial direction toward the rotation center axial line, respectively. The rotary door is disposed to be elastically deformable in such a manner that at least both parts of the side wall plates around the rotation center axial line are displaced away from each other by a dynamical pressure of a vehicle travelling, applied to the outer wall plate, in an inside air mode where the rotary door closes the outside air suction port and opens the inside air suction port. Further, the seal member press-contacts the inside/outside air switching box when at least both the parts of the side wall plates around the rotation center axial line are displaced away from each other by a predetermined distance. Thus, when the rotary door closes the outside air suction port and opens the inside air suction port in the inside air mode, the seal member press-contacts the inner surface of the inside/outside air switching box to seal a clearance between the inside/outside air switching box and the rotary door in the axial direction. Accordingly, in the inside air mode, it can prevent a leakage of outside air from the inside/outside air switching door (rotary door) into the inside/outside air switching box.
On the other hand, when the vehicle is travelling in low speed lower than a predetermined speed, the dynamical pressure in the vehicle travelling becomes lower. In this case, the displacement of the side wall plates due to the elastic deformation of the rotary door becomes smaller, and the seal member does not contact the inner surface of the inside/outside air switching box. However, because the dynamical pressure applied to the outer wall plate of the rotary door is small, a leakage of outside air into the inside/outside air switching box in the inside air mode can be substantially prevented. In this case, a sliding pressure of the rotary door can be reduced.
Preferably, in a natural state of the rotary door, both the side wall plates are tilted, respectively, toward the sides of the displacements, relative to a direction perpendicular to the outer wall plate. Therefore, a rotation moment generated to the side wall plates in the rotation direction of the rotary door can be increased, and the side wall plates can be readily displaced away from each other. More preferably, the tilt angle of each side wall plate is equal to or larger than 10 degrees.